Question: In history class, the girl to boy ratio is $9$ to $8$. If there are $36$ girls, how many boys are there?
Explanation: A ratio of $9$ girls to $8$ boys means that there is a group of $9$ girls for every group of $8$ boys. If there are $36$ girls, then there are $4$ groups of $9$ girls each. Because we know the ratio is $9:8$ , there must be $4$ groups of $8$ boys each. There is a total of $32$ boys in history class.